Watch: Matt Holliday collects career RBI No. 1000 in Cardinals' win

Welcome to the 1,000-RBI Club, Matt Holliday. With a bloop single to left-center field off the Mets' Jacob deGrom in the fifth inning of Monday night's 6-2 win in St. Louis, the Cardinals' outfielder became the 19th-active player to reach the 1,000-RBI plateau and the first since the Phillies' Ryan Howard did it just three weeks ago. The Oklahoma native finished the night 2-for-4 with a pair of singles, that RBI and a run scored.

For Holliday, the historic achievement comes in what's been a bit of a down year for the 34-year-old, with his season line sitting at .260/.376/.382 going into Monday night's action. That batting average and slugging percentage are both career-worsts. The OBP is his lowest mark since his second season in baseball back in 2005 with Colorado, and the .758 OPS would be the first time in 11 big league seasons he has failed to crack .800. At his current pace, Holliday would finish the season with a career-worst 12 homers. He's hit 22 or more the last seven seasons.

What's been eating at Holliday? For starters, his .292 BABIP is almost 50 points off his career mark of .341. Not once in his career has Holliday hit worse than .322 on balls in play, with that figure coming last year. His isolated power has dipped to .122, and his home runs-to-flyball ratio is half of what it's been in his career (7.0 vs. 15.7). Though Holliday is swinging less often than last year and still making the same amount of contact, he isn't doing much when he gets a pitch to hit.

While Holliday's bat can seemingly still handle the hard stuff (his .272 average and .444 slugging percentage on four-seamers this year isn't far off from his career marks of .283 and .479), he's getting eaten up by sinkers. His .297/.375 line on that pitch is a far cry from last year's .337/.500 and a career mark of .349/.521. That inability to pound sinking fastballs per usual has left him vulnerable to breaking pitches in particular, as he's hitting just .184 on sliders.

Also compounding matters is Holliday's increasing inability to hit left-handed pitching. On the season, the right-handed Holliday has just a .719 OPS against southpaws, the worst mark of his career. It's also the second straight season lefthanders have held Holliday under an .800 OPS; last year, he posted a .799 OPS against them in 144 plate appearances. Historically, Holliday has always hit righties better than lefties (a .917/.892 split in OPS), but his struggles this year have been particularly pronounced. What's interesting is that, repertoire-wise, left-handers haven't changed how they approach Holliday at all in the last four years. But as is the case overall, Holliday simply isn't picking up or doing damage to the sinker (.286 average against it vs. LHP), leaving him susceptible to the breaking ball (.083 vs. curveballs).

At 38-32 and leading the National League wild-card after Monday's win, the Cardinals have survived Holliday's season-long slump for now. But for a team that has gone from having the third-highest scoring offense in the league in 2013 (at 4.83 runs per game) to having MLB's fifth-worst this year (3.72), St. Louis needs its veteran slugger to start producing. Already, the team is suffering down years at the plate from Yadier Molina, Matt Carpenter and Allen Craig, and new additions like Jhonny Peralta and Kolten Wong haven't picked up the slack. At the very least, maybe the prospect of further climbing up the career RBI list can motivate Holliday. Currently tied for 276th on the all-time list with Darryl Strawberry, it's only another 1,297 RBI to tie Hank Aaron for first place.